Section 210.19 requires that the portion of a load that is continuous must be increased by 25% for establishing a minimum size of branch circuit conductor.

This minimum size is determined from Section 310.15 before the application of any correction or adjustment factors, using the assumed temperature rating of the terminal on the overcurrent device. This minimum conductor size can usually be determined by a simple look up from Table 310.15(B)(16). The correction and adjustment factors are used in determining the allowable ampacity of the conductor and in considering the temperature rating of the conductor (insulation), but they are not considered in establishing this specific minimum size.

The same requirement applies to sizing of the overcurrent device, but the rules are separated. Section 210.19 applies to conductors, and Section 210.20 applies to overcurrent devices. The result is that both conductors and overcurrent devices will have the same minimum rating.